1. Field of the Invention
The invention relates to a drum housing for a working drum of a construction machine or mining machine, said working drum being provided with tools and rotating about a drum axis with a specified rotating direction, a construction machine or mining machine with such drum housing, as well as a method for monitoring the condition of a working drum of a construction machine/mining machine or of the tools thereof arranged on the circumference of the working drum by measuring the condition of the working drum or the tools thereof by means of a monitoring device.
2. Description of the Prior Art
Such a method is known from DE 10 2008 045 470 A1 (US 2010/0076697). A monitoring device monitors the condition of the tools of a road milling machine by means of at least one inspection opening in a housing shell of a drum housing, said housing shell at least partially enclosing the circumference of the working drum.
The working drum of a construction machine, which is provided with tools and rotates about a drum axis, such as a milling drum during the working of road surfaces by means of road milling machines, as well as for the mining of deposits by means of surface miners, is subject to a continuous process of wear and tear, wherein a tool breakage may also occur. This concerns mainly the tools used, and in particular the milling tools, but also the toolholders. When the tools reach a certain state of wear, it is advisable to replace the tools as the ongoing process will otherwise lose in efficiency. In this regard, a distinction needs to be made between different states of wear which lead to the replacement of a milling tool or toolholder respectively:
1. Replacement of the milling tool as there is no longer sufficient wear material, especially carbide metal in the tip. The penetration resistance becomes too great, which leads to the efficiency decreasing as a result of excessive friction loss. Wear and tear is mainly rotationally symmetrical.2. Replacement of the toolholder as between the milling tool and holder, at the contact surface between these parts, wear and tear in particular of the holder occurs and the wear limit has been reached. This type of wear and tear is usually symmetrical.3. Non-rotationally symmetrical wear and tear of the milling tool tip and/or the milling tool head caused by insufficient rotational movement of the milling tool during the milling process. This results in a poor milling pattern and the risk of a tool breakage as the supporting effect of the milling tool head is lost.4. Furthermore, the toolholder may be subject to additional, non-rotationally symmetrical wear and tear.5. Milling tool breakage.
Furthermore, worn-out and/or broken milling tools can result in secondary damage to the toolholders, or worn-out toolholders, respectively, can result in secondary damage to the milling drum. Timely replacement of the milling tools and/or toolholders can therefore be necessary and reduce costs. Replacing the milling tools and/or toolholders too early, on the other hand, also means not working at optimal cost. In such a case, existing wear potential is not utilized appropriately. Previously, without any monitoring device, the state of wear of the milling drum and the tools, namely, the milling tools and toolholders, was assessed by means of a visual check performed by the machine operator. To do so, the machine operator needs to switch off the machine (turn off engine and uncouple drum from the drive train). He then needs to open the rear drum plate in order to visually inspect the milling drum.
The milling drum is then turned by means of a second drive (auxiliary drive) in order to be able to inspect, section by section, the entire milling drum. The task of inspecting the drum may also be undertaken by a second operator. In the process, the state of wear of the toolholders is usually assessed via so-called wear markings, while the state of wear of the milling tools is assessed via the wear in tool length and the rotational symmetry of the wear pattern.
Checking the state of wear of the milling tool and holder is very time-consuming and reduces the operating time of the machine. In addition, there is the risk, owing to the highly subjective assessment, that the state of wear of the holder and milling tool is not assessed correctly and the wear potential is therefore not optimally utilized.
According to the known prior art apparent from FIG. 2, a barrel of the inspection camera of the monitoring device is guided into the interior of the drum housing through an inspection opening in the housing shell of the drum housing. Furthermore, it is provided that the monitoring device is stowed in a protection device during the milling process. Owing to the circulating milled material, the barrel inside the drum housing is subject to a high degree of wear and tear and may be severely damaged by larger fragments of the milled material. Furthermore, damage to the optics of the camera through the barrel cannot be excluded if the camera is not demounted during the milling operation. The replacement of damaged parts is time-consuming. In addition, mounting time is incurred by the stowing, or mounting respectively, of the monitoring device.